Flow detection apparatus employing tire probes having ultrasonic oscilators mounted therein

ABSTRACT

An apparatus for detecting flaws using supersonic waves measures a thickness of a test object or a position of a cavity inside the test object by employing pair of ultrasonic probes. By changing a relative position of one ultrasonic probe to that of the other ultrasonic probe, a plurality of waveform data of ultrasonic reception signals is acquired. Each acquired waveform data is added per corresponding unit of time. Since a surface wave component of each waveform data has a shifted phase due to the difference in arrival time, a level of the surface wave component is offset and thus minimized through addition of the waveform data.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus for detecting a flaw usingsupersonic waves to perform non-destructive tests of civil engineeringand building structures such as asphalt paved roads, concrete pavedroads and external walls of tunnels using a low frequency ultrasonicwave, and more particularly, to an apparatus for detecting a flaw usingsupersonic waves to accurately measure defect positions and thicknesseswithout interference by a surface wave.

2. Description of the Related Art

Heretofore, apparatuses for detecting flaws using supersonic waves, usedfor non-destructive tests of civil engineering and building structuresand the like, infer internal states of whether defects such as cavitiesand the like exist by observing ultrasonic reception waveforms with anoscilloscope through disposing ultrasonic probes for transmission andfor reception in a predetermined distance with making water, glycerin,or the like lie between them and a test object. However, since a spotnon-destructive test cannot detect internal defects sufficiently andworks for changing a measuring point are complicated, the inventor etal., of the present invention have proposed an apparatus for detectingflaws using supersonic waves, i.e., the type of the system shown in FIG.1 (Japanese Patent Laid-Open No. Hei 5-080,035 published on March 30 in1994) that performs a non-destructive test of internal states of a civilengineering and building structure using a tire probe having built-inultrasonic probes for transmission and for reception.

In FIG. 1, a tire probe 302 is provided in free rotation inside a mainframe of an apparatus 300. The tire probe 302 is equipped with a rubbertire 304 made of hard urethane rubber, and a Gel sheet 306 outside thetire. As the Gel sheet 306, high polymer Gel of elastic can be used asdisclosed in, for example, Japanese Patent Laid-Open No. Hei 1-304,102.Both wheels of the rubber tires 304 are provided with a pivot 308 pereach, which is mounted on a probe mounting axle 312 fixed throughbearings 310 in free rotation in the main frame of the apparatus 300. Inaddition, an oil seal 314 is provided inside the bearings 310 so as toprevent outside leakage of medium liquid such as water and the like,filled in the rubber tire 304. A mounting frame 316 is attached to thecenter of the probe mounting axle 312, a ultrasonic probe fortransmission 318 and a ultrasonic probe for reception 320 are mounted onthe bottom of the mounting frame 316. From the ultrasonic probe fortransmission 318 and the ultrasonic probe for reception 320, signallines 322 and 324 are wired and connected to a transmission circuit anda receiving circuit respectively, both of which are not shown. Further,auxiliary wheels 326 are provided in the main frame of the apparatus 300so that stable running of the main frame of the apparatus 300 can beattained.

According to an apparatus for detecting flaws using supersonic wavesusing such a tire probe, by making the tire probe 302 run on a testobject, cross-sectional layer images showing a running distance in ahorizontal axis are displayed on a CRT monitor so that an internaldefect such as an cavity can be certainly found. However, in anapparatus for detecting flaws using supersonic waves using a tire probe,a surface waves propagated on near a surface of the test objectinterferes with reflective waves from acoustic discontinuous pointsinside the test object or from the bottom of the test object.Consequently, this lead to the problems that rise time and existing timeof the reflection waves in a reception waveform become unclear, thisgives great errors to precision of a non-destructive test, for example,identification of defect position inside the test object and thicknessmeasurement, and this causes impossible measurement.

For example, as shown in FIG. 2, the case that a non-destructive test isperformed through rotationally moving the tire probe 302 on a testsurface 320 of the test object 328 will be described. Ultrasonic wavestransmitted from the ultrasonic probe 318 for transmission built in thetire probe 302 pass a path of water of medium liquid (1), and apropagation path of longitudinal waves in an asphalt paved road (4) and(5), they arrive at the ultrasonic probe for reception 320 through apath in a tire (3), and the ultrasonic probe for reception obtainslongitudinal wave reflection echoes including information of thickness Hof the test object 328. At the same time, the ultrasonic wavestransferred from the ultrasonic probe 318 embedded the tire probe 302arrives at the ultrasonic probe for reception 320 through the path inthe water inside the tire (1), propagation path of the surface waves onthe test object 328 (2) and path in the water inside the tire (3). Inthis case, these waves do not include thickness information of theasphalt paved road, and interfere with the longitudinal wave reflectionecho as surface waves becoming disturbing waves upon thicknessmeasurement and the like. Consequently, a reception waveform becomes asshown in FIG. 3, the rise position of the bottom echo becomes unclear,and hence, these waves become obstacles to thickness measurement of thetest object.

Besides the tire probe, these conventional problems also arise atapparatuses for detecting flaw using supersonic wave adopting the typeof a ultrasonic probe that directly contacts to a test object with anacoustic Contact medium.

SUMMARY OF THE INVENTION

According to the present invention, an apparatus for detecting flawsusing supersonic wave and a tire probe, both of which make measurementof defect positions and thickness in high precision through removinginfluences of interference by surface waves, are provided. In anapparatus for detecting flaw using supersonic wave to measure thicknessof a test object, a cavity position inside the test object or the like,using a pair of ultrasonic probes, an apparatus according to the presentinvention for detecting flaw using supersonic wave changes relatively aposition of one ultrasonic probe against that of the other ultrasonicprobe, acquires a plurality of ultrasonic reception waveform data at aplurality of positions on the way of the change, and adds these waveformdata per corresponding time.

In addition, an apparatus according to the present invention fordetecting flaws using supersonic wave uses a tire probe as an ultrasonicprobe, which comprises a rotationally driving means for rotationallydriving independently a pair of tires mounting an ultrasonic oscillatorper each.

An apparatus according to the present invention for detecting flawsusing supersonic wave adopting a tire probe controls to fix one of apair of tires of a tire probe at a definite position on the test objectduring a definite period of measurement by a control means, and torotationally drive the other tire. During the subsequently definiteperiod, this controls to fix the tire having rotationally driven duringthe previously definite period at a definite position, and torotationally drive the other tire having fixed during the previouslydefinite period. A reception data acquisition memory means acquires andstores waveforms of ultrasonic reception signals at each of a pluralityof predetermined positions during each definite period. Finally, anadding means adds each waveform, acquired with the reception dataacquisition memory means, per corresponding time.

Further, after initializing with a control means so that a distancebetween both of tires becomes a predetermined value through locating atire probe at optionally designated position on a test object, anotherapparatus according to the present invention for detecting flaw usingsupersonic wave adopting the tire probe controls on the basis of theinitially set positions to rotationally drive a pair of tires on a testobject in order that the pair of tires run in definite but oppositedirections in same distance. In this case, a reception data acquisitionmemory means acquires and stores waveforms of ultrasonic receptionsignals at each of a plurality of predetermined positions, and an addingmeans adds each waveform, acquired with the reception data acquisitionmemory means, per corresponding time.

Furthermore, still another apparatus according to the present inventionfor detecting flaws using supersonic wave adopting a tire probe, as atire probe, comprises a pair of tires which mounts ultrasonicoscillators transmitting or receiving ultrasonic waves and are disposedon a line along the longitudinal direction of a frame on the frame, anda driving means for moving the frame on the test object throughrotationally driving one tire of the tire probe and for relativelymoving the pair of tires on the frame through rotationally driving theother tire. In this case, the control means controls to rotationallydrive one tire of the tire probe, to move the tire probe on the testobject, and simultaneously, to rotationally driving the other tire so asto change the distance to the former tire. A reception data acquisitionmemory means acquires and stores waveform data of ultrasonic receptionsignals at each of a plurality of predetermined positions duringrotational driving of a pair of tires by the control means. And, anadding means adds each waveform data, acquired with the reception dataacquisition memory means, per corresponding time.

Further, a further apparatus according to the present invention fordetecting flaws using supersonic wave uses an array type of ultrasonicoscillator composed of a plurality of element oscillators fortransmission and a plurality of element oscillators for reception, bothof which are located through acoustic connection medium on a testobject. Driving of each element oscillator is switched by a switchingmeans, and the switching means is controlled switching by a switchingcontrol means. Furthermore, A reception data acquisition memory meansacquires and stores waveform data of ultrasonic reception signals ateach of a plurality of positions of the array type of ultrasonicoscillators. And an adding means adds each waveform data, acquired withthe reception data acquisition memory means, per corresponding time.

Assuming that the number of the element oscillators is N, the switchingmeans in this case drives, as an oscillator for transmission, n piecesof element oscillators from the {(N/2)-n+1}th element oscillator to the(N/2)th one on the basis of its center, drives, as an oscillator forreception, n pieces of element oscillators from the {(N/2)+1}th elementoscillator to the {(N/2)+n}th one, and controls to switch each elementin a mirror image on the basis of its center in shifting one-by-one withelectronic scanning.

Further, a still further apparatus according to the present inventionfor detecting flaws using supersonic wave can be composed of a singleultrasonic oscillator having a predetermined area instead of a pluralityof element oscillators for transmission and residual element oscillatorsas the oscillator for reception.

Although such an apparatus for detecting flaw using supersonic wave anda tire probe acquire waveforms of ultrasonic reception signals at eachof a plurality of predetermined positions through relatively changing aposition of one ultrasonic probe or a tire probe against that of theother ultrasonic probe or tire probe, the distance between both ofultrasonic probes or tire probes is different at each time acquiredreception waveforms. Therefore, arrival time of surface waves, andarrival time of target echoes and bottom echoes at each time acquiredreception waveforms are also different. The arrival time of a surfacewave changes approximately proportionally to the distance betweenultrasonic probes or tires for transmission and reception. On the otherhand, although arrival time of a target echo and a bottom echo changeswith the distance between both ultrasonic probes or both tires, it isnot proportional to the distance, and variance of the arrival time of atarget echo in depth equal to or more than a definite value or a bottomecho in thickness equal to or more than a definite value is very smalleven if the distance between both ultrasonic probes or both tireschanges. Therefore, changing relatively a position of one ultrasonicprobe or one tire probe against that of the other ultrasonic probe orthe other tire probe, acquiring reception waveforms at a plurality ofpredetermined positions, and adding these waveforms per correspondingtime, a level of a surface wave component becomes low by phase cancelingeffect because of different arrival time. However, since the arrivaltime of the target echo or the bottom echo scarcely change, this echo isemphasized and its level increases. Consequently, measurement precisionof defect position and thickness can be greatly improved. In addition,in case, after initializing so that a distance between a pair ofultrasonic probes or tire probes becomes a predetermined value throughlocating them at optionally designated positions on a test object, anapparatus controls on the basis of the initially set positions so as tomake them in definite but opposite directions in same distance,cross-sectional layer images of the test object cannot be obtained, butthickness of a specific position of the test object can be measured moreaccurately.

The above and other objects, features, and advantages of the presentinvention will become more apparent from the following detaileddescription with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing a conventional tire probe;

FIG. 2 is an explanatory diagram showing propagation state of surfacewaves and longitudinal waves;

FIG. 3 is an explanatory diagram showing an interference region ofsurface waves;

FIG. 4 is a schematic structure and circuit block diagram of the firstembodiment of the present invention;

FIG. 5 is an explanatory diagram showing movement of a tire probe;

FIG. 6 is a graph showing relations of center-to-center distance betweenultrasonic oscillators for transmission and reception to degree of S/Nimprovement;

FIG. 7A to FIG. 7F show each reception waveform in case acenter-to-center distance is changed by 0.2 times of a wavelengthλ_(SAW) of a surface wave against a value L, and a waveform afteraddition of them;

FIG. 8 is a reception waveform graph in actual measurement;

FIG. 9A to 9C are model diagrams of propagation paths and propagationtime of bottom reflection echoes;

FIG. 10A to 10C are explanatory diagrams of the second embodiment of thepresent invention;

FIG. 11A to 11C are explanatory diagrams of ultrasonic measurement linesinside a test object.

FIG. 12A to 12C are explanatory diagrams of ultrasonic measurement linesinside a test object according to the first embodiment;

FIG. 13 is an explanatory diagram of the third embodiment of the presentinvention;

FIG. 14 is a schematic structure and circuit block diagram of the fourthembodiment of the present invention;

FIG. 15 is an explanatory diagram of an array type of ultrasonicoscillator used in the fourth embodiment;

FIG. 16 is an explanatory diagram of an array type of ultrasonicoscillator used in the fifth embodiment of the present invention;

FIG. 17 is a schematic structure and circuit block diagram of the sixthembodiment of the present invention;

FIG. 18 is an explanatory diagram of an array type of ultrasonicoscillator used in the sixth embodiment of the present invention;

FIG. 19 is an explanatory diagram of another array type of ultrasonicoscillator;

FIG. 20 is a schematic structure and circuit block diagram of theseventh embodiment of the present invention;

FIG. 21 is a schematic structure and circuit block diagram of the eighthembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 4 to FIGS. 9A-9C show the first embodiment of the presentinvention. In FIG. 4, ultrasonic oscillators 14 and 16 are embedded intires 10 and 12. In the tire 10 and 12, axles 18 and 20 are providedrespectively, and in the axles 18 and 20, driving gears 22 and 24 areprovided respectively. Stepping motors 26 and 28 have axles 30 and 32,and in the axles 30 and 32, driving gears 34 and 36 are provided.Between the driving gears 34 and 36 of the stepping motors 26 and 28 andthe driving gears 22 and 24 of the tires 10 and 12, driving belts 38 and40 are wrapped respectively. The stepping motors 26 and 28 arerotationally driven with motor driving circuits 42 and 44 respectively.These motor driving circuits 42 and 44, and stepping motors 26 and 28compose the driving means 46 for rotationally driving the tires 10 and12.

In addition, as shown in FIG. 5, the tires 10 and 12 are connected witha timing belt 45, and can move on a frame 48 with the driving means 46.The driving means 46, tires 10 and 12, ultrasonic oscillators 14 and 16,timing belt 45, and frame 48, as a whole, compose a tire probe 50.

The tires 10 and 12 are rotated with driving force of the stepping motor26 and 28. Since the stepping motor 26 and 28 can rotate or stop throughmotor controllers 54 and 56, and the motor driving circuits 42 and 44with commands of a control circuit 52 composed of a computer, they canbrake and stop the tires 10 and 12 at designated positions, androtationally move the tires to designated positions with commands fromthe control circuit 52. Further, the control circuit 52 can recognizethe positions of the tires 10 and 12 on the frame 48 with a rotaryencoder 58 and a counter 60. Thus, the counter 60 counts outputs of therotary encoder 58, and outputs the count to the control circuit 52. Thecontrol circuit 52 recognizes the positions of the tires 10 and 12 onthe frame 48 on the basis of the output of the counter 60, and controlsto brake, stop and rotationally drive the tires 10 and 12 with the motorcontroller 54 and 56, motor driving circuits 42 and 44, and steppingmotors 26 and 28. Therefore, the rotary encoder 58, counter 60, motorcontroller 54 and 56, and the control circuit 52 compose a control means62 for controlling the driving means 46. In the control circuit 52,programs to control the driving means 46 are embedded so that the tires10 and 12, and frame 48 operate on the test object 64 as states 1 to 9shown in FIG. 5.

Subsequently, movement of the tires 10 and 12, and frame 48 will bedescribed on the basis of FIG. 5. At first, if the tires 10 and 12, andframe 48 are set at the initial state with a command from the controlcircuit 52, the tires 10 and 12 are set at positioning relations of thestate 1 in FIG. 5 on the frame 48. Subsequently, if the tire 10 becomesin braking and stop with a command from the control circuit 52, the tire10 is locked at the current position on the test object 64 with thestepping motor 26. With setting the tire 10 in braking and stop, thetire 12 is rotationally moved with a command from the control circuit52, and then, positioning relations of the tires 10 and 12, and frame 48change from the state 1 to the state 5. In this time, since the tires 10and 12 are fixed to the timing belt 45 on the frame 48, and the tire 10is locked at one point on the test object 64, the frame 48 advances at ahalf speed of the tire 12 if the tire 12 advances.

When the state of the tire probe 50 arrives in the state 5, the tire 12is locked after braking and stop on the basis of a command from thecontrol circuit 52. Further, rotationally moving the tire 10 with acommand from the control circuit 52, positioning relations of the tires10 and 12, and frame 48 change from the state 5 to the state 9. Theframe 48 also advances at a half speed of the tire 10. Repeating suchoperations of the state 1-5 and state 5-9 in FIG. 5 alternatively, thetire probe 50 advances on the test object 64 at a half advancing speedof the tire 10 or 12.

Referring to FIG. 4 again, a ultrasonic oscillator 14 is disposeddownward in the tire 10, and as medium liquid, for example, water 66 isfulfilled. In addition, a ultrasonic oscillator 16 is disposed downwardin the tire 12, and as medium liquid, for example, water 68 isfulfilled. The ultrasonic oscillators 14 and 16 are connected to a pulsegenerator 76 for a pulse generation circuit or a receiver 78 forultrasonic wave reception circuit through signal lines 70 and 72, and atransmission/reception switching circuit 74. The transmission/receptionswitching circuit 74 switches to use either of the ultrasonic oscillator14 or ultrasonic oscillator 16 as that for transmission, and to use theother as that for reception with a command from the control circuit 52.

The pulse generator 76, on the basis of a trigger signal generated in atrigger generating circuit 80 with a command from the control circuit52, drives the ultrasonic oscillator 14 or 16 designated as that fortransmission with the transmission/reception switching circuit 74. Forexample, if the ultrasonic oscillator 14 is designated as that fortransmission and the ultrasonic oscillator 16 is designated as that forreception, the ultrasonic oscillator 14 generates pulsed ultrasonicwaves, and propagates them inside the test object 64. The ultrasonicwaves propagated inside the test object 64 arrives at the ultrasonicoscillator 16 through water 66 in the tire 10, and are received forconversion to electric signals. The received signals are amplified at apredetermined level with a receiver 78, after that, are converted todigital signals with an A/D converter 82 in the timing based on triggersignals generated in the trigger generating circuit 80, and are storedin a memory circuit 84. The reception data received in this time arewaveform data interfered with surface waves, target echoes inside thetest object, or bottom echoes, similarly to the reception waveform datain FIG. 3 that are obtained with a conventional tire probe. Thetransmission/reception switching circuit 74, pulse generator 74, triggergenerating circuit 80, receiver 78, A/D converter 86, memory circuit 84,and control circuit 52, as a whole, compose a reception data acquisitionmemory means 86 for acquiring and storing ultrasonic reception waveformdata from the ultrasonic oscillators 14 and 16 at a plurality ofpredetermined positions on the frame 48.

Still more, since the control circuit 52 has a function as an addingmeans 88, this adds each obtained reception waveform data percorresponding time. If the control circuit 52 adds each receptionwaveform data per corresponding time with the adding means 88, the levelof the surface wave component is lowered because of phase cancellationeffect derived from their different arrival time, while the level of thetarget echoes or the bottom echoes increases due to emphasis by additionbecause of little change of their arrival time. Thus, waveform datacomposed of depressed surface waves, and emphasized target echoes orbottom echoes can be obtained.

Here, a monitor 90 is connected to the control circuit 52, and on themonitor 90, cross-sectional layer images of the test object 64 showing arunning distance or position of the tire probe 50 in the horizontal axisand a depth in the vertical axis are displayed.

Subsequently, operations will be described. As shown in FIG. 4, it isdefined that the center-to-center distance between the ultrasonicoscillators 14 and 16 is L, and thickness of the test object 64 is H. Inaddition, it is also defined that the sonic velocity of longitudinalwaves 25 inside the test object 64 is V_(P), and the sonic velocity ofsurface waves 35 is V_(SAW). In this time, the arrival time t_(SAW) ofthe surface wave component included in the reception waveform data isexpressed as follows.

    t.sub.SAW =(L/V.sub.SAW)+τ                             (1)

In addition, the arrival time t_(P) of the bottom echo component derivedfrom the longitudinal waves included in the reception waveform data isexpressed as follows.

    t.sub.P ={(L.sup.2 +4H.sup.2).sup.1/2 /V.sub.P }+τ     (2)

Here, τ is the fixed delay time such as the fixed delay time arisen inthe ultrasonic oscillators 14 and 16, fixed delay time in pulsegenerator 54 and receiver 55, propagation time inside water in the tires10 and 12 and the like.

Then, if the center-to-center distance L between the ultrasonicoscillators 14 and 16 is changed, it is apparent from the expression (1)that the arrival time t_(SAW) of the surface wave component changesalmost proportionally to the distance L. On the other hand, it isapparent from the expression (2) that, if the center-to-center distanceL between the ultrasonic oscillators 14 and 16 is changed, the arrivaltime t_(P) of the bottom echo component does not change proportionally.For example, if thickness of the test object 64 is sufficiently large incomparison with the center-to-center distance L between the ultrasonicoscillators 14 and 16, and satisfies the following formula:

    H>>(L/2)                                                   (3)

the formula (2) can be expressed in the following formula:

    t.sub.P ={(4H.sup.2).sup.1/2 /V.sub.P }+τ=(2H/V.sub.P)+τ.(4)

Therefore, in this case, if the center-to-center distance L between theultrasonic oscillators 14 and 16 is changed, the arrival time t_(P) ofthe bottom echo component does not change.

It can be easily inferred that, if the center-to-center distance Lbetween the ultrasonic oscillators 14 and 16 is changed like this, thearrival time t_(SAW) of the surface wave component changes almostproportionally to the distance L, but change of the arrival time t_(P)of the bottom echo component is smaller than that of t_(SAW). Thus,during a definite period of measurement, for example, fixing one tire 10at a defiant position on the test object 64, rotationally moving theother tire 12, acquiring the ultrasonic reception waveform data at aplurality of predetermined positions, and adding each of these waveformdata per corresponding time, the arrival time t_(SAW) of the surfacewave component at each position of the tire 12 is different since thecenter-to-center distance L between the ultrasonic oscillators 14 and 16is different at each position of the tire 12, and hence, the amplitudeof the surface wave component after addition is depressed due to thephase canceling effect. On the other hand, since the arrival time t_(P)of the bottom echo component hardly changes at each position of the tire12, its amplitude increases with addition. Therefore, considering thesurface wave component as a noise component, and the bottom echocomponent as a signal component, in the reception waveform after theaddition processing, a S/N ratio is greatly improved, and hence, thebottom echo component in the reception waveform can be clarified.

Subsequently, relationship of tire movement to a degree of S/N ratioimprovement, clarified in investigation with simulation will bedescribed below.

The graph in FIG. 6 shows the relationship of the changed range of thecenter-to-center distance L between the ultrasonic oscillators 14 and 16in case of fixing a changing step of the center-to-center distance Lbetween the ultrasonic oscillators 14 and 16 by 0.1 times of awavelength λ_(SAW) of a surface wave, to a degree of S/N ratioimprovement. In this case, the changed step of the center-to-centerdistance L between the ultrasonic oscillators 14 and 16 is expressed inthe wavelength λ_(SAW) of a surface wave as a unit. Here, as an example,the case that thickness measurement is performed as the test object 64is a concrete block will be described. It is assumed that the sonicvelocity of a longitudinal wave in the concrete block is 3800 m/s, andthe propagation velocity of a surface wave is 2250 m/s. And, if thecenter frequency of the used ultrasonic pulses is assumed 70 kHz, thewavelength λ_(SAW) of a surface wave on the concrete block at 70 kHz:

    λ.sub.SAW =V.sub.SAW /f=2250[m/s]/70[kHz]=32[mm]    (5)

is obtained. Then, reception waveforms and an added waveform at eachposition in case of: using a tire probe 50 that the minimum value of thecenter-to-center distance between transmission and reception ultrasonicoscillators 14 and 16 is L_(min) =110 [mm]; braking and stopping thetire 10; rotationally moving the tire 12; increasing thecenter-to-center distance L between ultrasonic oscillators fortransmission and reception 14 and 16 by a step of 0.1 λ_(SAW) = 3.2[mm]; simulating to change the center-to-center distance L betweenultrasonic oscillators for transmission and reception 14 and 16:##EQU1## are shown in FIG. 7A to 7F. Here, FIG. 7A is in the case of L+0λ_(SAW), FIG. 7B is in the case of L+0.2_(SAW), FIG. 7C is in the caseof L+0.4λ_(SAW), FIG. 7D is in the case of L+0.6λ_(SAW), FIG. 7E is inthe case of L+0.8 λ_(SAW), and FIG. 7F is the added waveform of L+0λ_(SAW) to L+1.0 λ_(SAW). Since each reception waveform in FIG. 7A to 7Eis a resultant waveform interfered with surface waves and bottom echoes,identification of the surface waves and bottom echoes is necessary.Then, the waveform in FIG. 7F is obtained through adding each receptionwaveform data per corresponding time. Although this waveform afteraddition has residual surface waves, the surface waves are depressed,the S/N ratio is improved, and the bottom echoes are clearly emphasized.

FIG. 8 is an added waveform graph obtained in actual measurement, thebottom echoes become clear, and the first bottom reflection echoes (B1),second bottom reflection echoes (B2), and third bottom reflection echoes(B3) can be easily recognized. Here, the first bottom reflection echoes(B1), second bottom reflection echoes (B2), and third bottom reflectionechoes (B3) are, as in FIGS. 9A, 9B and 9C, the echoes that ultrasonicpulses radiated from the ultrasonic oscillator for transmission 14 arereflected one, two, and three times respectively on the bottom of theconcrete block of the test object 64 on the way to the ultrasonicoscillator for reception 16. The rise time of the first bottomreflection echoes, second bottom reflection echoes, and third bottomreflection echoes coincide well with the following calculated value ofpropagation time of each echo. Using the propagation paths of the firstbottom reflection echoes, second bottom reflection echoes, and thirdbottom reflection echoes in FIGS. 9A, 9B, and 9C and the sonic velocityof a longitudinal wave, their propagation time t_(P1), t_(P2), andt_(P3) calculated from the expression (2) become respectively asfollows.

t_(P1) =120 to 122 μs

t_(P2) =223 to 224 μs

t_(P3) =327 to 328 μs

The reason why each propagation time has a range is correspondence tochanging of the center-to-center distance L between the ultrasonicoscillators for transmission and reception 14 and 16 from 110 mm to 142mm. Although, as for the first bottom reflection echoes in FIG. 8, theirpropagation time becomes slightly unclear due to interference with theresidual surface waves, it can be surely considered as the first bottomreflection echoes because of the calculated values of the propagationtime of the echoes, the calculated values attached to the model drawingsin FIG. 9A to 9C.

Then, if, in FIG. 9A to 9C, the center-to-center distance L between theultrasonic oscillators for transmission and reception 14 and 16, sonicvelocity V_(P) of longitudinal waves inside the test object 64, andfixed delay time are already known, calculation of the thickness H ofthe test object 64 becomes possible, since the unknown number becomesonly the thickness H of the test object 64 if the propagation timet_(P1), t_(P2), and t_(P3) are measured from the reception waveform.

Therefore, for example, if, in the transition process from the state 1to the state 3 in movement of the tire probe 50 in FIG. 5,above-mentioned acquisition and addition processing of the receptionwaveforms are performed, it becomes possible to measure the averagethickness of the test object, e.g., concrete in this section withoutinterference of the surface waves. Similarly, if, in the transitionprocess from the state 3 to the state 5, acquisition and additionprocessing of the reception waveforms are performed, it becomes possibleto measure the average thickness of the test object in this sectionwithout interference of the surface waves. If, in each process of tiremovement, the thickness of the test object 64, e.g., concrete ismeasured similarly to this, it becomes possible to measure the averagethickness H of the test object along the running loci of the tire probe50 without interference of the surface waves.

In addition, in case that a defect such as a cavity and the like existsinside the test object 64 under the running loci of the tire probe 50,its depth can be measured. Further, if the occurred positions of echoesare plotted on a monitor 90 showing a running distance or position ofthe tire probe 50 in the horizontal axis and a depth of the test object64 in the vertical axis, a cross-sectional layer image of the testobject 64 like that in FIG. 4 can be displayed. In this manner,measurement precision of inside defect position and thickness can begreatly improved.

Subsequently, the second embodiment of the present invention will bedescribed, referring to FIG. 10A to 10C, FIG. 11, and FIG. 12. In thefirst embodiment, a tire probe was described, the tire probe comprisinga driving means 46 for rotationally driving independently a pair oftires 10 and 12 mounting an apparatus for detecting flaw usingsupersonic wave and ultrasonic oscillators 14 and 16, the apparatus fordetecting flaw using supersonic wave comprising: a control means forcontrolling to fix the tire 10 of the tires at a definite position onthe test object 64 during a definite period of measurement by a controlmeans, and to rotationally drive the other tire 12, during thesubsequently definite period, to fix the tire 12 having rotationallydriven during the previously definite period at a definite position, andto rotationally drive the other tire 10 having fixed during thepreviously definite period; a reception data acquisition memory means 86for acquiring and storing waveforms of ultrasonic reception signals ateach of a plurality of predetermined positions during each definiteperiod; further, an adding means 88 for adding each reception waveformdata per corresponding time.

On the other hand, the second embodiment is characterized in a controlmeans for controlling to initially set a distance between both of tires10 and 12 at a predetermined value through locating tire probes atoptionally designated positions on a test object, and to rotationallydrive, on the basis of the initially set positions, a pair of tires 10and 12 on a test object 64 in order that the pair of tires run indefinite but opposite directions in same distance. In addition, areception data acquisition memory means 86 and an adding means 60 aresame as those in the first embodiment.

Using the same configuration as that of the apparatus according to thefirst embodiment for detecting flaw using supersonic wave, the apparatusaccording to the second embodiment for detecting flaw using supersonicwave can be realized through only changing steps of driving control ofthe tires 10 and 12. Then, operations of the tires 10 and 12, and frame48 will be described on the basis of FIG. 10A to 10C. At first, with acommand from the control circuit 52, the tires 10 and 12, and frame 48are initially set at optionally designated positions on the test object64 as the state 1 in FIG. 10A so as that the distance between both oftires 10 and 12 becomes minimum. In this state 1, ultrasonic oscillators14 or 16 mounted in the tires 10 or 12 is driven with a pulse generator76 on the basis of trigger signals generated with a trigger generatingcircuit 80 by the control circuit 52, and radiates ultrasonic waves intothe test object 64. Further, the ultrasonic waves arrive at theultrasonic oscillator 16 or 14 mounted in the tire 12 or 10 from thetest object 64, and are received. Subsequently, according to a commandfrom the control circuit 52, the tires 10 and 12 is rotationally drivenon the basis of the initial set positions in order that the tires arelocated in definite but opposite directions in the same distance on atest object, and becomes position relationship at the state 2 in FIG.11B. In this time, similarly to the state 1 in FIG. 11A, the ultrasonicoscillator 14 or 16 mounted in the tires 10 or 12 is driven with a pulsegenerator 76 on the basis of trigger signals generated with a triggergenerating circuit 80 by the control circuit 52, and radiates ultrasonicwaves into the test object 64. Further more, the ultrasonic waves arriveat the ultrasonic oscillator 16 or 14 mounted in the tire 12 or 10 fromthe test object 64, and are received.

Still more, similarly to above, according to a command from the controlcircuit 52, the tires 10 and 12 is rotationally driven on the basis ofthe initial set positions in order that the tires are located indefinite but opposite directions in the same distance on a test object,and have positioning relations of the state 3 in FIG. 11C. In this time,similarly to the state 1 in FIG. 11A, the ultrasonic oscillator 14 or 16mounted in the tires 10 or 12 is driven with a pulse generator 76 on thebasis of trigger signals generated with a trigger generating circuit 80by the control circuit 52, and radiates ultrasonic waves into the testobject 64. Further more, the ultrasonic waves arrive at the ultrasonicoscillator 16 or 14 mounted in the tire 12 or 10 from the test object64, and are received.

In this manner, after initializing with a control means so that adistance between both of tires becomes a predetermined value atoptionally designated positions on a test object, this apparatuscontrols to rotationally drive, on the basis of the initial setpositions, the pair of tires 10 and 12 in order that the tires arelocated in definite but opposite directions in the same distance on atest object, acquires and stores waveforms of ultrasonic receptionsignals at each of a plurality of predetermined positions inrotationally driving of the tires 10 and 12, and finally, adds eachacquired waveform per corresponding time. Adding these waveforms percorresponding time, a level of a surface wave component becomes low byphase canceling effect because of different arrival time. However, sincethe arrival time of the target echo or the bottom echo scarcely changes,this echo is emphasized and its level increases. Consequently,measurement precision of a defect position and thickness can be greatlyimproved.

Ultrasonic measurement lines in the test object in this time are asshown in FIG. 11A to 11C. All the measurement lines become onesreflected at the same point R on the bottom surface of the test object.Hence, in this embodiment, thickness of the test object at the point Rcan be measured accurately. Here, in FIG. 11A to 11C,

T21 (1) shows the center position of the tire 10 at the state 1;

T21 (2) shows the center position of the tire 10 at the state 2;

T21 (3) shows the center position of the tire 10 at the state 3;

T22 (1) shows the center position of the tire 12 at the state 1;

T22 (2) shows the center position of the tire 12 at the state 2;

T22 (3) shows the center position of the tire 12 at the state 3;

L1 shows a ultrasonic wave propagation path at the state 1;

L2 shows a ultrasonic wave propagation path at the state 2;

L3 shows a ultrasonic wave propagation path at the state 3;

"R" shows a ultrasonic wave reflection point on the bottom surface;

"92" shows the top surface of the test object 64;

"94" shows the bottom surface of the test object 64.

On the other hand, ultrasonic measurement lines in the test object 64 inthe first embodiment are as shown in FIGS. 12A to 12C. Followingmovement of the tires 10 and 12, the ultrasonic wave reflection pointmoves from R1 to R2 and R3. Therefore, in the first embodiment, onlyaverage thickness of the bottom surface B from R1 to R3 can be measured.Here, in FIGS. 12A to 12C,

R1 shows a ultrasonic wave reflection point at the state 1 in FIG. 5;

R2 shows a ultrasonic wave reflection point at the state 2 in FIG. 5;

R3 shows a ultrasonic wave reflection point at the state 3 in FIG. 5.

In the second embodiment, although cross-sectional layer images of thetest object 64 cannot be displayed in running because of movement mannerof the tires 10 and 12, this is suitable to accurate measurement ofthickness at the specific position of the test object 64. Then, a methodthat, after grasping the outline of the test object 64 in the firstembodiment, only particularly necessary positions are precisely measuredin the second embodiment can be considered.

FIG. 13 shows the third embodiment of the present invention, and this ischaracterized in arrangement of the tires 10 and 12 on a line along theadvancing direction of the frame 48. The tire 12 is mounted to the frame48 in free rotation, its position is fixed, and rotation of the tire 12can move the frame 48. On the other hand, the tire 10 is driven with atiming belt and the like, and can change its position relatively inrotationally moving to the frame 48. Therefore, the tires 10 and 12 areon a line, and further, can mutually change their space relatively. Ingeneral, a sound field of ultrasonic waves (sound strength distribution)transmitted from and received to a tire probe has a characteristicdepending on a radiating direction also in a horizontal plane. Againstthis, in the third embodiment, since the direction of the wavestransmitted from and received to the tire probe for transmission andreception is fixed, this has an advantage that this is not affected tothe direction dependency of the tire probe in the horizontal plane.

FIG. 14 and FIG. 15 show the fourth embodiment of the present invention.FIG. 14 shows an entire structure of an apparatus according to thepresent invention for detecting flaw using supersonic wave, and FIG. 15shows an array type of ultrasonic oscillator used in the fourthembodiment. In this fourth embodiment, especially in the case notrequiring a cross-sectional layer image of the test object, theconfiguration and operations of an apparatus for detecting flaw usingsupersonic wave for attaining the objects of the present invention willbe described.

In FIG. 14, an array type of ultrasonic oscillator 104 is located on asurface of a test object 100 through acoustic connection medium 102 suchas water, jelly, Gel, oil and the like. The array type of ultrasonicoscillator 104 is composed of N pieces of ultrasonic oscillators, i.e.,element oscillators. The n pieces of element oscillators from the firstelement oscillator to the nth one are used for transmission, and npieces of element oscillators, for example, from the kth elementoscillator to the (k+n-1)th one are used for reception.

The array type of ultrasonic oscillator 104, as shown in FIG. 15, iscomposed of N pieces of rectangular element oscillators, one of whichhas an element width w and a length (width of the oscillator) W, at apitch p in a line arrangement. Here, "C" shows a ultrasonic oscillatorfor transmission, "D" shows a ultrasonic oscillator for reception, L_(C)shows a center-to-center distance between ultrasonic oscillators fortransmission and reception, L_(T) shows a length of the ultrasonicoscillator for transmission C, L_(R) shows a length of the ultrasonicoscillator for reception D, and "E" shows the scanning direction of theultrasonic oscillator for reception D. Therefore, if the ultrasonicoscillator for reception D is scanned along the scanning direction E oneby one, the center-to-center distance L_(C) between ultrasonicoscillators for transmission and reception changes by the pitch p.

Each element oscillator of the array type of ultrasonic oscillator 104is connected to a multiplexer for transmission and reception 110respectively through signal lines 108. The multiplexer for transmissionand reception 110 is connected to a pulse generator 114 throughreception terminals 112. Further, the multiplexer for transmission andreception 110 is also connected to a receiver 118 through receptionterminals 116. Furthermore, the multiplexer for transmission andreception 110 is connected to a control circuit 122 through an interfacecircuit 120, and is performed switching control by the control circuit122. The interface circuit 120 and control circuit 122, as a whole,compose a switching control means 124.

Based on a trigger signal generated in the trigger generating circuit126 through the interface circuit 120 with a command from the controlcircuit 122, the pulse generator 114 drives the element oscillators fortransmission designated with the multiplexer for transmission andreception 110. If, by the multiplexer for transmission and reception110, the element oscillators for reception is designated, the elementoscillators for transmission generate pulsed ultrasonic waves, andpropagate the ultrasonic waves into the test object 100 through acousticconnection medium 102. The ultrasonic waves propagated inside the testobject 100 arrive at the element oscillators for reception, and arereceived.

After the received reception waveform data are amplified to thepredetermined level in the receiver 118, they are converted to digitalsignals in an A/D converter 128 in the timing based on a trigger signalgenerated in the trigger generating circuit 126, and are stored in amemory circuit 130 through the interface circuit 120. The pulsegenerator 114, trigger generating circuit 126, receiver 118, A/Dconverter 128, interface circuit 120, memory circuit 130, and controlcircuit 122, as a whole, compose a reception data acquisition memorymeans 132 for acquiring and storing reception waveform data from thearray type of ultrasonic oscillators 104 at a plurality of positions.

Since the control circuit 122 has a function as an adding means 134,this adds each obtained reception waveform data per corresponding time.If the control circuit 122 adds each reception waveform data percorresponding time with the adding means 134, the level of the surfacewave component is lowered due to phase cancellation effect derived fromtheir different arrival time, while the level of the target echoes orthe bottom echoes increases due to emphasis by addition because oflittle change of their arrival time.

Next, operations of the fourth embodiment will be described. Themultiplexer for transmission and reception 110 connects the pulsegenerator 114 to n pieces of element oscillators from the first elementoscillator to the nth one through the transmission terminals 112 with acommand from the control circuit 122. Similarly, the multiplexer fortransmission and reception 110 connects the receiver 118 to n pieces ofelement oscillators from the kth element oscillator to the (k+n-1)th onethrough the reception terminals 116 with a command from the controlcircuit 122. The pulse generator 114 is always connected to the n piecesof element oscillators from the first element oscillator to the nth one.The receiver 118 is connected to n pieces of element oscillators, forexample, from the (n+1)th element oscillator to the 2nth one inmeasurement start timing, In this time, if the trigger generatingcircuit 126 generates a trigger signal after reception of a command fromthe control circuit 122 through the interface circuit 120, the pulsegenerator 114 drives n pieces of element oscillators from the firstelement oscillator to the nth one on the basis of this trigger signal,and radiates ultrasonic waves into the test object 100.

The ultrasonic waves propagated inside the test object 100 arrive at then pieces of element oscillators from the (n+1)th element oscillator tothe 2nth one, and are received. After the received reception waveformsignals are amplified to the predetermined level with the receiver 118,they are converted to digital signals in the A/D converter 128 in thetiming based on a trigger signal generated in the trigger generatingcircuit 126, and are stored in the memory circuit 130. The receptionwaveform data received in this time are the waveform data interferedwith surface waves and target echoes inside the test object or bottomechoes, similarly to the conventional reception waveform data in FIG. 3.After the reception waveform data are stored in the memory circuit 130,the multiplexer for transmission and reception 110 connects the receiver118 to n pieces of element oscillators from the (n+2)th elementoscillator to the (2n+1)th one through the reception terminals 116 witha command from the control circuit 122. Further, by the same manner, thereceived waveforms are converted to digital signals, and are stored inthe memory circuit 130. Furthermore, this apparatus shifts n pieces ofelement oscillators for reception one-by-one with electronic scanning,and repeats this processing until the nth element oscillator becomes theNth element oscillator. If this apparatus shifts n pieces of elementoscillators for reception one-by-one with this scanning, thecenter-to-center distance L_(C) between the element oscillators fortransmission and reception changes by the pitch p. Therefore, if, usingthe adding means 134 of the control circuit 122, this apparatus addseach obtained reception waveform data per corresponding time, because ofthe same principle as that of the first embodiment, the level of thesurface wave component is lowered due to phase cancellation effectderived from their different arrival time, while the level of the targetechoes or the bottom echoes increases due to emphasis by additionbecause of little change of their arrival time. Thus, waveform datacomposed of depressed surface waves, and emphasized target echoes orbottom echoes can be obtained.

In this fourth embodiment, similarly to the first embodiment, ultrasonicmeasurement lines inside the test object 100 are shown in FIG. 12A toFIG. 12C. Thus, as this apparatus shifts the element oscillators forreception on-by-one with the electronic scanning, the reflection pointmoves from R1 to R2 and further R3. Therefore, in the third embodiment,only average thickness of the bottom surface B of the test object 106from R1 to R3 can be measured.

Subsequently, FIG. 16 shows an array type of ultrasonic oscillator 104used in the fifth embodiment of the present invention. Although thefifth embodiment can be realized with the same apparatus as that of thefourth embodiment according to the present invention, the electronicscanning manner of the element oscillator for transmission is differentfrom that of the element oscillator for reception.

In the fifth embodiment, as shown in FIG. 16, at measurement start, thisapparatus uses n pieces of element oscillators from the {(N/2)-n+1}element oscillator to the (N/2)th one as a ultrasonic oscillator fortransmission on the basis of its center (the center line G ofoscillators in FIG. 16). In addition, this uses n pieces of elementoscillators from the {(N/2)+1}th element oscillator to the {(N/2)+n}thone as an oscillator for reception. Still more, as the measurementprocessing advances, this controls to switch each element used fortransmission and each element for reception in a mirror image on thebasis of its center in shifting one-by-one with electronic scanning.Here, "F" shows the scanning direction of the ultrasonic oscillator fortransmission C, and "E" shows the scanning direction of the ultrasonicoscillator for reception D.

If, using the adding means 134 provided in the control circuit 122 inFIG. 14, this apparatus adds each obtained reception waveform data percorresponding time, because of the same principle as that of the fourthembodiment, the level of the surface wave component is lowered due tophase cancellation effect derived from their different arrival time,while the level of the target echoes or the bottom echoes increases dueto emphasis by addition because of little change of their arrival time.Thus, waveform data composed of depressed surface waves, and emphasizedtarget echoes or bottom echoes can be obtained. Ultrasonic measurementlines in the test object 106 in this time are as shown in FIG. 11A to11C. All the measurement lines become ones reflected at the same point Ron the bottom surface of the test object 100. Hence, in this embodiment,thickness of the test object 100 at the point R can be measuredaccurately. Consequently, the fifth embodiment can measure the thicknessof the specific position on the test object 100 in precision higher thanthe fourth embodiment.

Subsequently, FIG. 17 to FIG. 19 show the sixth embodiment of thepresent invention. FIG. 17 shows an entire structure of an apparatusaccording to the sixth embodiment for detecting flaw using supersonicwave, FIG. 18 shows an array type of ultrasonic oscillator, and FIG. 19shows a modified example of an array type of ultrasonic oscillator usedin the sixth embodiment.

In FIG. 17, an array type of ultrasonic oscillator 150 is located on asurface of a test object 100 through acoustic connection medium 102.This array type of ultrasonic oscillator 150 replaces n pieces ofelement oscillator from the first element oscillator to the nth one, toa single ultrasonic oscillator for transmission 152 having apredetermined area, and uses residual element oscillators as oscillatorsfor reception. The residual element oscillators for reception areconnected through signal lines 108 to a multiplexer for reception 154being a switching means. The multiplexer for reception 154 is connectedto a receiver 118 through reception terminals 116. The ultrasonicoscillator for transmission 152 is directly driven with a pulsegenerator 114.

At the ultrasonic oscillator for transmission 150 in FIG. 18 and FIG.19, the center-to-center distance L_(c) between the ultrasonicoscillator 152 composed of, for example, element oscillators from thekth element oscillator to the (k+4)th one and the ultrasonic oscillatorfor reception D changes by the pitch p, if the element oscillators ofthe ultrasonic oscillator for reception D are shifted one-by-one. Here,L_(C) min in FIG. 19 shows the shortest center-to-center distancebetween the ultrasonic oscillators for transmission and reception. And,the sixth embodiment can obtain the same effect as the fourthembodiment.

FIG. 20 shows an apparatus according to the seventh embodiment fordetecting flaw using supersonic wave. The seventh embodiment is also anexample of the case not especially requiring a cross-sectional layerimage of the test object. One ultrasonic probe 158, for example, aultrasonic probe for transmission is fixed on the test object 100through an acoustic connection medium 156. Thus, one ultrasonic probe158 is fixed on a frame 160, and is fixed at the optional position to bedesired to measure, on the test object 100. The other ultrasonic probe162, for example, a ultrasonic probe for reception, is connected to abelt 164. The belt 164 is wrapped between driving gears 166 and 168, thedriving gear 166 is connected to a stepping motor 170, and the drivinggear 168 is connected to a rotary encoder 172. The stepping motor 170 isdriven a motor driving circuit 174, and the motor driving circuit 174 iscontrolled by a motor controller 176. The belt 164, driving gears 166and 168, stepping motor 170, motor driving circuit 174 and motorcontroller 176, as a whole, compose a driving means 178. The ultrasonicprobe 162 can move on the frame 160 with the driving means 178. Thus,the ultrasonic probe 162 contacts to the surface of the test object 100through an acoustic medium 180, and can move on a definite range of thetest object 100 that is limited with a frame 160. In other words, sincethe stepping motor 170 can rotate and stop with a command from thecontrol circuit 122 through the interface circuit 120, motor controller176 and motor driving circuit 174, this can brake and stop theultrasonic probe 162 connected to the belt 164 at the designatedposition, and can move it to the designated position.

In addition, the control circuit 122 can recognize a position of theultrasonic probe 162 on the frame 160, that is, a position of theultrasonic probe 162 on the test object 100 with a rotary encoder 172and a counter 182. The rotary encoder 172 analyses rotation of thedriving gear 168, the counter 182 counts an output of the rotary encoder172, and outputs to the control circuit 122 through the interfacecircuit 120. The control circuit 122, based on the output of the counter182, recognizes a position of the frame 160 of the ultrasonic probe 162on the test object 100, controls the driving means 178, and controlsbraking, stopping and moving of the ultrasonic probe 162. Therefore, therotary encoder 172, counter 182, interface circuit 120, and controlcircuit 122, as a whole, compose a control means 184 for controlling thedriving means 178.

The ultrasonic probe 158 is driven with a pulse signal generated in apulse generator 114, i.e., a pulse generating circuit, the pulsegenerator 114 outputs a pulse signal through the interface circuit 120with a trigger signal generated in the trigger generating circuit 126with a command from the control circuit 122. Ultrasonic waves radiatedfrom the ultrasonic probe 158 propagates into the test object 100through the acoustic medium 156, arrives at the ultrasonic probe 162through the acoustic medium 180, and are received. After the receivedwaveform signals are amplified to the predetermined level with thereceiver 118, they are converted to digital signals in the A/D converter128 in the timing based on a trigger signal generated in the triggergenerating circuit 126, and are stored in the memory circuit 130.Therefore, the pulse generator 114, trigger generating circuit 126,receiver 118, A/D converter 128, memory circuit 130, interface circuit120, and control circuit 122, as a whole, compose a reception dataacquisition memory means 186 for acquiring and storing ultrasonicreception waveform data at a plurality of positions on the frame 160.

In addition, since the control circuit 122 has a function as an addingmeans 188, this adds each obtained reception waveform data percorresponding time. If the control circuit 122 adds each receptionwaveform data per corresponding time with the adding means 188, thelevel of the surface wave component is lowered due to phase cancellationeffect derived from their different arrival time, while the level of thetarget echoes or the bottom echoes increases due to emphasis by additionbecause of little change of their arrival time. Thus, waveform datacomposed of depressed surface waves, and emphasized target echoes orbottom echoes can be obtained. Hence, using the seventh embodiment,similarly to the above-mentioned embodiments, changing relatively aposition of the ultrasonic probe 158 against that of the ultrasonicprobe 162, acquiring ultrasonic reception waveforms at a plurality ofpredetermined positions on the way of changing, and adding thesewaveforms per corresponding time, a level of a surface wave component,which becomes an interfering wave, is depressed, but a level of a targetecho or a bottom echo is emphasized through addition and its levelincreases. Thus, waveform data composed of depressed surface waves, andemphasized target echoes or bottom echoes can be obtained, and hence,measurement precision of inside defect position and thickness can begreatly improved.

FIG. 21 shows an apparatus according to the eighth embodiment of thepresent invention for detecting flaw using supersonic wave. This eighthembodiment is also an example of the case not especially requiring across-sectional layer image of the test object. Although, in the seventhembodiment, one ultrasonic probe is fixed and the other ultrasonic probemoves, the eighth embodiment changes the relative distance between bothultrasonic probes through moving both ultrasonic probes.

In FIG. 21, one ultrasonic probe, for example, a ultrasonic probe fortransmission 200 is located on the test object 100 through the acousticconnection medium 156. The ultrasonic probe 200 is connected to a belt202. The belt 202 is wrapped between driving gears 204 and 206, thedriving gear 204 is connected to a stepping motor 208, and the drivinggear 206 is connected to a rotary encoder 210. The stepping motor 204 isdriven a motor driving circuit 212, and the motor driving circuit 212 iscontrolled by a motor controller 214. The belt 202, driving gears 204and 206, stepping motor 204, motor driving circuit 212 and motorcontroller 214, as a whole, compose a driving means 216.

The ultrasonic probe 200 can move on the frame 218 with the drivingmeans 216. Thus, the ultrasonic probe 200 contacts to the surface of thetest object 100 through an acoustic medium 156, and can move on adefinite range of the test object 100 that is limited with a frame 218.In other words, the stepping motor 204 can rotate and stop with acommand from the control circuit 186 through the interface circuit 120,motor controller 214 and motor driving circuit 212. Therefore, this canbrake and stop the ultrasonic probe 200 connected to the belt 202 at thedesignated position, and can move it to the designated position.

In addition, the control circuit 186 can recognize a position of theultrasonic probe 200 on the frame 218, that is, a position of theultrasonic probe 200 on the test object 100 with a rotary encoder 210and a counter 220. The rotary encoder 210 analyses rotation of thedriving gear 206. The counter 220 counts an output of the rotary encoder210, and outputs to the control circuit 186 through the interfacecircuit 120. The control circuit 186, based on the output of the counter220, recognizes a position of the ultrasonic probe 200 on the frame 218,i.e., a position on the test object 100, controls the driving means 216,and controls braking, stopping and moving of the ultrasonic probe 200.Therefore, the rotary encoder 210, counter 220, interface circuit 120,and control circuit 186, as a whole, compose a control means 222 forcontrolling the driving means 216. In this manner, in the eighthembodiment, one ultrasonic probe 200 and the other ultrasonic probe 162can move on the frame 218, and can obtain similar measurement result tothe seventh embodiment through changing the relative distance betweenthe ultrasonic probes 200 and 162.

In this manner, changing relatively a position of one ultrasonic probeor one tire probe against that of the other ultrasonic probe or theother tire probe, acquiring ultrasonic reception waveforms at aplurality of predetermined positions, and adding these waveforms percorresponding time, a level of a surface wave component becomes low byphase canceling effect because of different arrival time. However, sincethe arrival time of the target echo or the bottom echo scarcely changes,this echo is emphasized and its level increases. Consequently,measurement of a defect position and thickness of the test object can beperformed in high precision without interference of surface waves.

In case, after initially setting a distance between a pair of ultrasonicprobes or tire probes at a predetermined value through locating the pairof ultrasonic probes or tire probes at optionally designated positionson a test object, this apparatus controls, on the basis of the initialset positions, the pair in order that the pair are located in definitebut opposite directions in the same distance on a test object, this canmeasure thickness at the specific position of the test object moreaccurately than the others, although this cannot detect cross-sectionallayer images of the test object.

Further, the present invention is not limited by the numbers shown inembodiments.

What is claimed is:
 1. A flaw detection apparatus, comprising:a tireprobe comprising a pair of tires having respective ultrasonicoscillators mounted therein, each of said ultrasonic oscillators fortransmitting or receiving ultrasonic waves applied to a test object, anda driving means for rotationally driving each of said tiresindependently to change a relative position therebetween; a controlmeans for controlling said driving means to alternately rotate and fixsaid pair of tires during each of successive definite periods such thata one of said pair of tires is rotated in one definite period while theother of said pair of tires is fixed in said one definite period, andsuch that said one of said pair of tires is fixed in a next definiteperiod while said other of said pair of tires is rotated in said nextdefinite period; a reception data acquisition memory means for acquiringand storing waveform data of ultrasonic reception signals at each of aplurality of predetermined relative positions of said pair of tiresduring each of said definite periods; an adding means for adding eachwaveform data per corresponding time, said waveform data acquired withsaid reception data acquisition memory means.
 2. An apparatus accordingto claim 1, wherein said driving means is a stepping motor.
 3. Anapparatus according to claim 1, wherein said control means includes arotary encoder for detecting a rotational amount of each of said pair oftires.
 4. An apparatus according to claim 1, wherein said adding meansis a computer.